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Вычисление CRC32 на Lua

Опубликовано в QLua

Функция вычисления CRC32 на Lua

function crc32(buf, size)
   local crc = 0xFFFFFFFF
   local table = {}
   local rem, c
 
   -- calculate CRC-table
   for i = 0, 0xFF do
      rem = i
      for j = 1, 8 do
         if (rem & 1 == 1) then
            rem = rem >> 1
            rem = rem ~ 0xEDB88320
         else
            rem = rem >> 1
         end
      end
      table[i] = rem
   end
 
   for x = 1, size do
      c = buf[x]
      crc = (crc >> 8) ~ table[(crc & 0xFF) ~ c]
   end
   return crc ~ 0xFFFFFFFF
end

 

Как её использовать:

 

local str = "Это строка с какой-то очень умной мыслью"
local t = {}
for i = 1, #str do
 t[i] = str:byte(i)
end
 
print(string.format("CRC32: %x", crc32(t,#str)))

 

 

При каждом вызове высчитывать матрицу - неправильная история. Укажем циферки явно и вообще причешем:

 

 

crc32 = {
   _tbl = { 
          [0] = 0,0x77073096,0xEE0E612C,0x990951BA,0x76DC419,0x706AF48F, 0xE963A535,0x9E6495A3,0xEDB8832, 0x79DCB8A4,   -- 0 
       0xE0D5E91E,0x97D2D988,0x9B64C2B,0x7EB17CBD, 0xE7B82D07,0x90BF1D91,0x1DB71064,0x6AB020F2,0xF3B97148,0x84BE41DE, -- 10 
       0x1ADAD47D,0x6DDDE4EB,0xF4D4B551,0x83D385C7,0x136C9856,0x646BA8C0,0xFD62F97A,0x8A65C9EC,0x14015C4F,0x63066CD9, -- 20 
       0xFA0F3D63,0x8D080DF5,0x3B6E20C8,0x4C69105E,0xD56041E4,0xA2677172,0x3C03E4D1,0x4B04D447,0xD20D85FD,0xA50AB56B, -- 30 
       0x35B5A8FA,0x42B2986C,0xDBBBC9D6,0xACBCF940,0x32D86CE3,0x45DF5C75,0xDCD60DCF,0xABD13D59,0x26D930AC,0x51DE003A, -- 40 
       0xC8D75180,0xBFD06116,0x21B4F4B5,0x56B3C423,0xCFBA9599,0xB8BDA50F,0x2802B89E,0x5F058808,0xC60CD9B2,0xB10BE924, -- 50 
       0x2F6F7C87,0x58684C11,0xC1611DAB,0xB6662D3D,0x76DC4190,0x1DB7106, 0x98D220BC,0xEFD5102A,0x71B18589,0x6B6B51F,  -- 60 
       0x9FBFE4A5,0xE8B8D433,0x7807C9A2,0xF00F934, 0x9609A88E,0xE10E9818,0x7F6A0DBB,0x86D3D2D, 0x91646C97,0xE6635C01, -- 70 
       0x6B6B51F4,0x1C6C6162,0x856530D8,0xF262004E,0x6C0695ED,0x1B01A57B,0x8208F4C1,0xF50FC457,0x65B0D9C6,0x12B7E950, -- 80 
       0x8BBEB8EA,0xFCB9887C,0x62DD1DDF,0x15DA2D49,0x8CD37CF3,0xFBD44C65,0x4DB26158,0x3AB551CE,0xA3BC0074,0xD4BB30E2, -- 90 
       0x4ADFA541,0x3DD895D7,0xA4D1C46D,0xD3D6F4FB,0x4369E96A,0x346ED9FC,0xAD678846,0xDA60B8D0,0x44042D73,0x33031DE5, -- 100 
       0xAA0A4C5F,0xDD0D7CC9,0x5005713C,0x270241AA,0xBE0B1010,0xC90C2086,0x5768B525,0x206F85B3,0xB966D409,0xCE61E49F, -- 110 
       0x5EDEF90E,0x29D9C998,0xB0D09822,0xC7D7A8B4,0x59B33D17,0x2EB40D81,0xB7BD5C3B,0xC0BA6CAD,0xEDB88320,0x9ABFB3B6, -- 120 
       0x3B6E20C, 0x74B1D29A,0xEAD54739,0x9DD277AF,0x4DB2615, 0x73DC1683,0xE3630B12,0x94643B84,0xD6D6A3E, 0x7A6A5AA8, -- 130 
       0xE40ECF0B,0x9309FF9D,0xA00AE27, 0x7D079EB1,0xF00F9344,0x8708A3D2,0x1E01F268,0x6906C2FE,0xF762575D,0x806567CB, -- 140 
       0x196C3671,0x6E6B06E7,0xFED41B76,0x89D32BE0,0x10DA7A5A,0x67DD4ACC,0xF9B9DF6F,0x8EBEEFF9,0x17B7BE43,0x60B08ED5, -- 150 
       0xD6D6A3E8,0xA1D1937E,0x38D8C2C4,0x4FDFF252,0xD1BB67F1,0xA6BC5767,0x3FB506DD,0x48B2364B,0xD80D2BDA,0xAF0A1B4C, -- 160 
       0x36034AF6,0x41047A60,0xDF60EFC3,0xA867DF55,0x316E8EEF,0x4669BE79,0xCB61B38C,0xBC66831A,0x256FD2A0,0x5268E236, -- 170
       0xCC0C7795,0xBB0B4703,0x220216B9,0x5505262F,0xC5BA3BBE,0xB2BD0B28,0x2BB45A92,0x5CB36A04,0xC2D7FFA7,0xB5D0CF31, -- 180
       0x2CD99E8B,0x5BDEAE1D,0x9B64C2B0,0xEC63F226,0x756AA39C,0x26D930A, 0x9C0906A9,0xEB0E363F,0x72076785,0x5005713,  -- 190
       0x95BF4A82,0xE2B87A14,0x7BB12BAE,0xCB61B38, 0x92D28E9B,0xE5D5BE0D,0x7CDCEFB7,0xBDBDF21, 0x86D3D2D4,0xF1D4E242, -- 200
       0x68DDB3F8,0x1FDA836E,0x81BE16CD,0xF6B9265B,0x6FB077E1,0x18B74777,0x88085AE6,0xFF0F6A70,0x66063BCA,0x11010B5C, -- 210
       0x8F659EFF,0xF862AE69,0x616BFFD3,0x166CCF45,0xA00AE278,0xD70DD2EE,0x4E048354,0x3903B3C2,0xA7672661,0xD06016F7, -- 220
       0x4969474D,0x3E6E77DB,0xAED16A4A,0xD9D65ADC,0x40DF0B66,0x37D83BF0,0xA9BCAE53,0xDEBB9EC5,0x47B2CF7F,0x30B5FFE9, -- 230
       0xBDBDF21C,0xCABAC28A,0x53B39330,0x24B4A3A6,0xBAD03605,0xCDD70693,0x54DE5729,0x23D967BF,0xB3667A2E,0xC4614AB8, -- 240
       0x5D681B02,0x2A6F2B94,0xB40BBE37,0xC30C8EA1,0x5A05DF1B,0x2D02EF8D                                                                       -- 250 }, 

_calc = 
          function(self,str) 
                local crc = 0xFFFFFFFF 
                local tbl = self._tbl 
                local byte = string.byte

                str:gsub(".", 
                             function(x) 
                                     crc = (crc >> 8) ~ tbl[(crc & 0xFF) ~ byte(x)] 
                             end
                            ) 
                return crc ~ 0xFFFFFFFF 
          end 
} 

local crc32 = setmetatable(crc32, { __call = crc32._calc } )

 

Использование очевидно:

 

print(crc32("Сходят с ума только те, у кого он есть. Станислав Ежи Лец"))

Архив QLua